1. Field of the Invention
The present invention relates to a transporting apparatus for conveying a member by means of an endless belt, and an image-forming apparatus using the transporting apparatus.
2. Description of Related Art
As is known in the art, in an image-forming apparatus such as copiers or printers, a recording medium like recording paper or cloth is transported to a recording means where desired image is recorded on the recording medium, and thereafter further transported so as to be discharged therefrom. The transportation of the recording medium is generally carried out such that the recording paper is grasped between a pair of rollers and conveyed thereby. Alternatively, in the case where cloth or the like is used as the recording medium, the cloth is adhered to a rotating endless belt spanned under tension between drive and driven rollers, so as to be transported therewith.
In the transporting apparatus using th(e afore-mentioned endless belt, the recording medium is tensioned (back tension) on a side of a feeding roller so as not to cause wrinkles on the recording medium when the recording medium is fixedly adhered onto the endless belt. For this reason, when the endless belt is constructed by a non-metallic member, there arises such a problem that the tension force exerted on the endless belt by the tensioned recording medium induces undesired elongation of the endless belt so that the transportation accuracy of the recording medium tends to be adversely affected.
In order to prevent the adverse influence due to the tension force exerted by the recording medium, the drive and driven rollers are coupled with a D.C. motor, a pulse generator, a digital servo mechanism or the like to control the transportation. However, these devices and mechanisms or control methods therefor are complicated.
On the other hand, when the endless belt is constructed by a rigid metallic member, such an endless belt exhibits a small elongation when exposed to the tension force by the recording medium. However, the metallic endless belt is expensive, resulting in increased production cost of the apparatus as a whole.
Further, in addition to the adverse influence by the back tension, if the apparatus becomes large in size, the rotation of the driven roller creates a large inertia force, so that only the driven roller is continuously rotated by the effect of the inertia force even when the drive roller is stopped. This tends to deteriorate the transportation accuracy.